Diacetylene compounds are known as extremely unique substances capable of forming crystalline polymers upon solid phase polymerization by heat, light, .gamma.-rays, etc. and are expected to serve as photoelectronic materials, such as conductive materials, chromism materials, photoelectric materials, non-linear optical materials, and the like. For example, it is predicted that these compounds show a ultra-high speed switch phenomenon in the order of about 10.sup.-12 second by their non-linear optical effects and, therefore, they are promising for application to photo information processing systems.
In application to these fields, particularly the non-linear optical field, it is important to fabricate the diacetylene compound into a molecular orientated film having satisfactory crystallinity and orientation. Satisfactory crystalline films, namely molecular orientated films are also utilizable as light waveguide. Thus, possibilities of broad and various applications of the molecular orientated films are opened.
Japanese Laid-Open Patent Application No. 62608/84 discloses a process for producing a thin film of a diacetylene polymer which comprises forming a thin film of a diacetylene monomer on a base by spraying or spinning a solution or suspension of a diacetylene compound or by vacuum depositing the diacetylene compound, followed by polymerization.
However, it is generally impossible to orientate the diacetylene compound by this process. Moreover, the resulting film has very poor crystallinity, namely involves many brawbacks, such as cracks, a domain structure, a stacking disorder, and poor evenness of the plane.
In order to eliminate these drawbacks, Macromolecules, Vol. 18, 2341-2344 (1985) teaches that a diacetylene compound is heated to a temperature above its melting point and a shear force is applied thereto to thereby induce orientation and crystallization of the molecules. In some cases, however, the diacetylene compound undergoes thermal polymerization on elevation of temperature, resulting in incomplete shearing orientation, bringing disadvantages such as no improvement on crystallinity and orientation, etc. Besides, the resulting film is limited in thickness and area.
On the other hand, there are many reports about a film forming process including building up of a diacetylene compound having both a hydrophobic group and a hydrophilic group according to a Langmuir-Blodgett method. These processes enable us to control stacking in the thickness direction but still fail to orientate the molecules. Therefore, the resulting film is poor in crystallinity, involving disadvantages such as a domain structure, etc.
It has also been reported in Die Makromolekulare Chemie: Rapid Communications, Vol. 5, 77-81 (1984) that a polydiacetylene cast film formed on a transparent base is rubbed to orientate the main chain. This technique is, however, limited in material and film thickness. That is, employable materials are limited to few soluble polydiacetylenes and the process is only applicable to production of a very thin film. Further, the resulting film is not uniform and extremely inferior in orientation and crystallinity.
Hence, there has not yet been developed an excellent process for producing a molecular orientated film, by which the photoelectronic functions possessed by polydiacetylene can be made the best possible use of. Development of such a process has been a point of importance.